/**
 * @createTime: 2018年3月14日
 * @copyright: 上海道枢信息技术有限公司
 */
package com.mti.zhpt.utils;

import org.springframework.stereotype.Component;

/**
 * 主键ID生成工具
 * @classDesc: 功能描述: twitter的snowflake算法 -- java实现
 * @author binrui.dong
 * @createTime 2018年3月14日 上午9:53:35
 * @version v1.0.0
 * @copyright: 上海道枢信息技术有限公司
 */
@Component
public class SnowFlake {

	/**
	 * 起始的时间戳
	 */
	private final static long START_STMP = 1480166465631L;

	/**
	 * 每一部分占用的位数
	 */
	private final static long SEQUENCE_BIT = 12; // 序列号占用的位数
	private final static long MACHINE_BIT = 5; // 机器标识占用的位数
	private final static long DATACENTER_BIT = 5;// 数据中心占用的位数

	/**
	 * 每一部分的最大值
	 */
	private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
	private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
	private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

	/**
	 * 每一部分向左的位移
	 */
	private final static long MACHINE_LEFT = SEQUENCE_BIT;
	private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
	private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

	private long datacenterId; // 数据中心
	private long machineId; // 机器标识
	private long sequence = 0L; // 序列号
	private long lastStmp = -1L;// 上一次时间戳

	public SnowFlake(long datacenterId, long machineId) {
		if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
			throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
		}
		if (machineId > MAX_MACHINE_NUM || machineId < 0) {
			throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
		}
		this.datacenterId = datacenterId;
		this.machineId = machineId;
	}
	
	public SnowFlake() {}


	/**
	 * 产生下一个ID
	 *
	 * @return
	 */
	public synchronized String nextId() {
		long currStmp = getNewstmp();
		if (currStmp < lastStmp) {
			throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
		}

		if (currStmp == lastStmp) {
			// 相同毫秒内，序列号自增
			sequence = (sequence + 1) & MAX_SEQUENCE;
			// 同一毫秒的序列数已经达到最大
			if (sequence == 0L) {
				currStmp = getNextMill();
			}
		} else {
			// 不同毫秒内，序列号置为0
			sequence = 0L;
		}

		lastStmp = currStmp;

		return String.valueOf((currStmp - START_STMP) << TIMESTMP_LEFT // 时间戳部分
                | datacenterId << DATACENTER_LEFT // 数据中心部分
                | machineId << MACHINE_LEFT // 机器标识部分
                | sequence); // 序列号部分
	}

	/**
	 * @return the datacenterId
	 */
	public long getDatacenterId() {
		return datacenterId;
	}

	/**
	 * @param datacenterId the datacenterId to set
	 */
	public void setDatacenterId(long datacenterId) {
		this.datacenterId = datacenterId;
	}

	/**
	 * @return the machineId
	 */
	public long getMachineId() {
		return machineId;
	}

	/**
	 * @param machineId the machineId to set
	 */
	public void setMachineId(long machineId) {
		this.machineId = machineId;
	}

	private long getNextMill() {
		long mill = getNewstmp();
		while (mill <= lastStmp) {
			mill = getNewstmp();
		}
		return mill;
	}

	private long getNewstmp() {
		return System.currentTimeMillis();
	}

	public static void main(String[] args) {
		SnowFlake snowFlake = new SnowFlake(2, 3);
		System.out.println((1 << 12));
		for (int i = 0; i <3; i++) {
			System.out.println(snowFlake.nextId());
		}

	}

}
